I've got a home brewed RTC with DS1307. I've put two pullup resistors on SDA and SCL lines, connected them to the Arduino 5 and 6 pin respectively. I've also provided a backup battery since I read sometimes the RTC can hang if there is not a proper backup voltage. The arduino program hangs on the instruction:
int err = Wire.endTransmission();
I guess there is no reply from the device so SW wait indefinitely.
Strangely if I remove the I2C conenctions, endOfTrasmission returns a NACK error code ( I say strangely because I better expect an hang without any device connected ).
I have no idea on what to test, I suspect the DS1307 being damaged by some adventurous test in swapping
A5-A6 data but I have no idea of how to make this diagnosis.